Mr Gething’s campaign was marred by headlines about £200,000 of cash from Dauson Environmental Group, owned by a man twice prosecuted for environmental offences
Welsh government minister and Miles supporter, Julie James called for a review of how leadership campaigns would be run in the future.
Mark Drakeford is expected to resign on Tuesday after his final First Minister’s Questions in the Senedd. Mr Gething will replace him the following day.
Born to a Welsh father and a Zambian mother, Mr Gething pursued a legal career before being elected to the Welsh Parliament in 2011.
The Cardiff South and Penarth Member of the Senedd (MS) is currently economy minister in Mr Drakeford’s cabinet, and celebrated his 50th birthday on Friday.
Mr Starmer said Mr Gething would “lead a hopeful, ambitious Welsh Labour government, in the face of a tired and failed Tory government in Westminster”.
The prime minister said on X, formerly known as Twitter, Mr Gething’s election was “a chance for a new Welsh administration to focus on what matters to people in Wales”.
As soon as the announcement had been made, Mr Gething received a huge hug from his young son.
Mr Miles left the Cardiff University building where the result was announced without speaking to the media.
He later issued a written statement congratulating Mr Gething but, in what might be an allusion to the row over donations, said Welsh Labour leaders must continuously earn the trust of the public.
In his acceptance speech, Mr Gething praised his predecessor, describing Mr Drakeford as the “right leader at the right time in the pandemic”.
He also praised his rival, Mr Miles, who would have been Wales’ first gay leader if he had been the victor.
Mr Gething said the education minister had given a “new hope” to Welsh boys and girls “who might have otherwise thought very differently about public life here”.
Turning to his victory, he said: “Today, we turn a page in the book of our nation’s history.
“Not just because I have the honour of becoming the first black leader in any European country – but because the generational dial has jumped too.”
He also emphasised his commitment to devolution, calling it “not something I have had to get used to or adapt to or apologise for”.
“Devolution – Welsh solutions to Welsh problems – that’s in my blood. It’s what I’ve always known.”
In his statement, Mr Miles said: “I congratulate Vaughan on his election. I wish him every success for Wales’ future.”
He said he was proud he secured support “from a clear majority of Welsh Labour Senedd members, council leaders and deputies, CLPs [Constituency Labour Parties], and across our trades unions, MPs, peers and the all member vote of the Co-operative Party”.
In what might be a reference to the controversy over donations to the new Welsh Labour leader’s campaign, Mr Miles said serving the people of Wales was “an honour and responsibility underpinned by trust that must be continually earned”.
